audio_dac.h (5739B)
1 /* Copyright 2019 Jack Humbert 2 * Copyright 2020 JohSchneider 3 * 4 * This program is free software: you can redistribute it and/or modify 5 * it under the terms of the GNU General Public License as published by 6 * the Free Software Foundation, either version 2 of the License, or 7 * (at your option) any later version. 8 * 9 * This program is distributed in the hope that it will be useful, 10 * but WITHOUT ANY WARRANTY; without even the implied warranty of 11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 12 * GNU General Public License for more details. 13 * 14 * You should have received a copy of the GNU General Public License 15 * along with this program. If not, see <http://www.gnu.org/licenses/>. 16 */ 17 #pragma once 18 19 #ifndef A4 20 # define A4 PAL_LINE(GPIOA, 4) 21 #endif 22 #ifndef A5 23 # define A5 PAL_LINE(GPIOA, 5) 24 #endif 25 26 /** 27 * Highest value allowed sample value. 28 29 * since the DAC is limited to 12 bit, the absolute max is 0xfff = 4095U; 30 * lower values adjust the peak-voltage aka volume down. 31 * adjusting this value has only an effect on a sample-buffer whose values are 32 * are NOT pregenerated - see square-wave 33 */ 34 #ifndef AUDIO_DAC_SAMPLE_MAX 35 # define AUDIO_DAC_SAMPLE_MAX 4095U 36 #endif 37 38 #if !defined(AUDIO_DAC_SAMPLE_RATE) && !defined(AUDIO_MAX_SIMULTANEOUS_TONES) && !defined(AUDIO_DAC_QUALITY_VERY_LOW) && !defined(AUDIO_DAC_QUALITY_LOW) && !defined(AUDIO_DAC_QUALITY_HIGH) && !defined(AUDIO_DAC_QUALITY_VERY_HIGH) 39 # define AUDIO_DAC_QUALITY_SANE_MINIMUM 40 #endif 41 42 /** 43 * These presets allow you to quickly switch between quality settings for 44 * the DAC. The sample rate and maximum number of simultaneous tones roughly 45 * has an inverse relationship - slightly higher sample rates may be possible. 46 * 47 * NOTE: a high sample-rate results in a higher cpu-load, which might lead to 48 * (audible) discontinuities and/or starve other processes of cpu-time 49 * (like RGB-led back-lighting, ...) 50 */ 51 #ifdef AUDIO_DAC_QUALITY_VERY_LOW 52 # define AUDIO_DAC_SAMPLE_RATE 11025U 53 # define AUDIO_MAX_SIMULTANEOUS_TONES 8 54 #endif 55 56 #ifdef AUDIO_DAC_QUALITY_LOW 57 # define AUDIO_DAC_SAMPLE_RATE 22050U 58 # define AUDIO_MAX_SIMULTANEOUS_TONES 4 59 #endif 60 61 #ifdef AUDIO_DAC_QUALITY_HIGH 62 # define AUDIO_DAC_SAMPLE_RATE 44100U 63 # define AUDIO_MAX_SIMULTANEOUS_TONES 2 64 #endif 65 66 #ifdef AUDIO_DAC_QUALITY_VERY_HIGH 67 # define AUDIO_DAC_SAMPLE_RATE 88200U 68 # define AUDIO_MAX_SIMULTANEOUS_TONES 1 69 #endif 70 71 #ifdef AUDIO_DAC_QUALITY_SANE_MINIMUM 72 /* a sane-minimum config: with a trade-off between cpu-load and tone-range 73 * 74 * the (currently) highest defined note is NOTE_B8 with 7902Hz; if we now 75 * aim for an even even multiple of the buffer-size, we end up with: 76 * ( roundUptoPow2(highest note / AUDIO_DAC_BUFFER_SIZE) * nyquist-rate * AUDIO_DAC_BUFFER_SIZE) 77 * 7902/256 = 30.867 * 2 * 256 ~= 16384 78 * which works out (but the 'scope shows some sampling artifacts with lower harmonics :-P) 79 */ 80 # define AUDIO_DAC_SAMPLE_RATE 16384U 81 # define AUDIO_MAX_SIMULTANEOUS_TONES 8 82 #endif 83 84 /** 85 * Effective bit-rate of the DAC. 44.1khz is the standard for most audio - any 86 * lower will sacrifice perceptible audio quality. Any higher will limit the 87 * number of simultaneous tones. In most situations, a tenth (1/10) of the 88 * sample rate is where notes become unbearable. 89 */ 90 #ifndef AUDIO_DAC_SAMPLE_RATE 91 # define AUDIO_DAC_SAMPLE_RATE 44100U 92 #endif 93 94 /** 95 * Size of the dac_buffer array. This controls the length of the runtime buffer 96 * which accumulates the data to be sent to the DAC every few milliseconds, and 97 * it does not need to correspond to the length of the wavetable for the chosen 98 * waveform defined by AUDIO_DAC_SAMPLE_WAVEFORM_* in the additive DAC driver. 99 * By default, this is set to be as close to 3.3 ms as possible, giving 300 DAC 100 * interrupts per second. Any smaller and the interrupt load gets too heavy and 101 * this results in crackling due to buffer underrun in the additive DAC driver; 102 * too large and the RAM (additive driver) or flash (basic driver) usage may be 103 * too high, causing build failures, and matrix scanning is liable to have long 104 * periodic pauses that delay key presses or releases or fully lose short taps. 105 * Large buffers also cause notes to take longer to stop after they should from 106 * music mode or MIDI input. 107 * This should be a power of 2 for maximum compatibility. 108 */ 109 #ifndef AUDIO_DAC_BUFFER_SIZE 110 # if AUDIO_DAC_SAMPLE_RATE < 5100U 111 # define AUDIO_DAC_BUFFER_SIZE 16U 112 # elif AUDIO_DAC_SAMPLE_RATE < 9900U 113 # define AUDIO_DAC_BUFFER_SIZE 32U 114 # elif AUDIO_DAC_SAMPLE_RATE < 19500U 115 # define AUDIO_DAC_BUFFER_SIZE 64U 116 # elif AUDIO_DAC_SAMPLE_RATE < 38700U 117 # define AUDIO_DAC_BUFFER_SIZE 128U 118 # else 119 # define AUDIO_DAC_BUFFER_SIZE 256U 120 # endif 121 #endif 122 123 /** 124 * The number of tones that can be played simultaneously. If too high a value 125 * is used here, the keyboard will freeze and glitch-out when that many tones 126 * are being played. 127 */ 128 #ifndef AUDIO_MAX_SIMULTANEOUS_TONES 129 # define AUDIO_MAX_SIMULTANEOUS_TONES 2 130 #endif 131 132 /** 133 * The default value of the DAC when not playing anything. Certain hardware 134 * setups may require a high (AUDIO_DAC_SAMPLE_MAX) or low (0) value here. 135 * Since multiple added sine waves tend to oscillate around the midpoint, 136 * and possibly never/rarely reach either 0 of MAX, 1/2 MAX can be a 137 * reasonable default value. 138 */ 139 #ifndef AUDIO_DAC_OFF_VALUE 140 # define AUDIO_DAC_OFF_VALUE AUDIO_DAC_SAMPLE_MAX / 2 141 #endif 142 143 #if AUDIO_DAC_OFF_VALUE > AUDIO_DAC_SAMPLE_MAX 144 # error "AUDIO_DAC: OFF_VALUE may not be larger than SAMPLE_MAX" 145 #endif 146 147 /** 148 *user overridable sample generation/processing 149 */ 150 uint16_t dac_value_generate(void);